The Santa Fe's destination, or car cards as they called them, were 3x3 inch manila cardstock. On them, the had the initial location (in the case of the ones I've researched Los Angeles), a date, zone number/terminal destination (ie, Kansas City), car initials, number, contents and destination (ie, ABC Grocers).
Those of you who've seen my presentation on the Patch at Naperville or elsewhere, saw the film "Assembling a Freight Train," which showed the industry clerk tacking them to the sides of the cars, referred to as "carding the car." In the film, the clerk used the side of flat nosed pliers to tack the card.
On my website, www.patchrailroad.net, under Patch Operations, I have some photos taken from the film, a picture of a card and some additional explanation. In the 2012 issue of Great Model Railroads, my article on the Patch has a sidebar on how I use the car cards in operation.
Keith Jordan